This invention generally relates to combination lock systems and to the construction of tumbler wheels in combination locks that are designed to permit changing combination of such locks.
Similar to many prior art combination locks, the tumbler wheels have gates in the outside edge of the wheels. Because of the relationship between adjacent tumbler wheels, as the combination lock is turned in one direction and then the other, one or more of the wheels are rotated until all of the gates are aligned, and an arm can fit into the gates. This either permits the bolt to be released or the arm may contact a pawl which opens the bolt upon further rotation of the dial.
The combination of such locks can be adjusted by having a two-piece tumbler wheel with a drive ring or member and a gate ring mounted concentrically around the drive member. The drive member fixed to the dial, and the gate ring is normally locked in place on the drive member so that they rotate together. Upon release of a cam or other member the gate ring can rotate around the drive member so that the position of the gate can be altered with respect to the position of the dial. U.S. Pat. No. 4,142,388 (1979) to Peter Phillips as well as some of the prior art cited therein have adjustable gate rings.
In the past, although plastic has been suggested because the tumbler wheel does not carry large loads, the tumbler wheels have generally been constructed of metal. Machining of metal is costly, however, and it is also heavier so that it has greater inertia requiring more force to start and stop rotation. Another problem with metal tumbler wheels is that they can be observed through x-rays. As thieves and other unauthorized persons become more sophisticated, some have resorted to using x-rays to determine the position of the tumbler wheels. Plastic is generally transparent to x-rays so that it cannot be observed. Also unlike plastic, some metals are also magnetic, and thieves may magnetically manipulate some tumblers.
Therefore, it is an object of the present invention to disclose and provide a tumbler wheel construction in which the gate ring is formed of plastic. Another object of the present invention is to disclose and provide a tumbler wheel that is easily manufactured. In many of the prior art devices, the mechanism for releasing the gate member from the drive means was exceedily complex and required assembling many subparts. Injenction molded plastic meets these criteria.
In the aforementioned Phillips patent, the gate ring is secured to the drive member by means of an integral arm which is normally resiliently biased to the securing position. A key or cam can urge the leg out of engagement with the drive member, but other than the leg's resiliency, nothing other than removing the key or cam is necessary to secure the leg to the drive member. Resiliency is thus important, but need not be used only to urge a leg against the drive member only to be overcome by a cam; the resiliency could also urge a leg away from the drive member and the cam could overcome this resiliency positioning the leg against the drive member. Without resiliency the leg would have to be moved by a cam or other mechanical device both against the drive member and away from it. In a small diameter, thin gate ring made of plastic, it would be difficult to provide sufficient biasing with a single leg construction. Therefore, one of the objects of the present invention is to disclose and provide a construction for the gate ring with sufficient resiliency.
Another problem in the prior art, albeit minor, has been in determining whether the gate ring is locked with respect to the drive member. This is sometimes difficult to do visually assuming that the tumbler wheels are visible. It is an object, therefore, of the present invention to disclose and provide indicia that will permit visual inspection to determine whether the gate ring is locked to the drive member.
These objects are met by the present invention, which also meets other objects that, although not set forth specifically herein, are evident from the description of the invention.